This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The present disclosure relates generally to leak tolerant liquid cooling systems for electrical components.
In the prior art, such liquid cooling systems are described in U.S. Pat. No. 4,698,728 (“the '728 patent”) and U.S. Pat. No. 5,048,599 (“the '599 patent”), which are hereby incorporated by reference for all their teachings relating to leak tolerant liquid cooling systems for electrical components.
In the '728 patent, a liquid coolant is directed past the electrical components via certain conduits at sub-atmospheric pressure. Since the pressure of the liquid inside of the conduits is less than the pressure of the atmosphere outside the conduits, air gets sucked into the conduits if they develop a leak. Consequently, none of the liquid coolant is spilled. However, after the air gets into the conduits, it must somehow be purged from them. Otherwise, if the air is allowed to remain entrained in the coolant, the rate at which the coolant moves through the system would be reduced which in turn would reduce the systems cooling ability. Additionally, accumulation of air in the system can cause a coolant reservoir of the system to overflow. Further, the air could get trapped in certain critical passages of the cooling system, such as passages in a cooling jacket around the electrical components, which in turn would cause hot spots in the cooling system.
In the '728 patent, a mechanism by which air is removed from the coolant is illustrated and described in conjunction with FIGS. 2a-2d. However, with that mechanism, a pump which circulates the liquid coolant through the conduits must be temporarily turned off and then turned back on in order to perform the air purging operation. Such an interruption in the operation of the pump may temporarily lower the rate at which the coolant flows through the system, which in turn lowers the rate at which the electrical components are cooled. In addition, switching the pump from off to on produces pressure surges throughout the cooling circuit, and that in turn stresses the cooling circuit components and their joints. Further, switching the pump from off to on produces a step like increase in electrical power which is drawn from the cooling system's power supply. Thus, the power supply must include compensation to insure that harmful transients do not occur in any supply voltages to the electrical components that are being cooled.
The '599 patent describes one solution to this issue. In the system described therein, a leak tolerant liquid cooling system for electrical components includes a cooling circuit which contains a pump and conduits that circulate a liquid coolant past the electrical components and through the bottom chamber of a purge tank. This purge tank also has a top chamber which is connected to the bottom chamber through a passageway; and, the bottom chamber is sized such that the liquid coolant passes through it with a velocity which is low enough to let any air bubbles in the coolant rise and move by buoyancy through the passageway into the top chamber. Also, the top chamber has an input port and an output port with respective valves. Air is purged from the top chamber through the output port by forcing liquid coolant into the top chamber from a reservoir via the input port. As this occurs, the coolant continues to be pumped past the electrical components through the coolant circuit. Thus, the pressures throughout the cooling circuit remains constant, and the supply voltages to the electrical components remain constant. Also, to purge air from the top chamber quickly, the passageway between the purge tank chambers is constricted in a way which hinders the flow of coolant from the top chamber to the bottom chamber while the coolant is being forced into the top chamber.
However, in the system of the '599 patent, there are valves and/or orifices that are internal to the purge tank and/or the reservoir. Therefore, the reservoir and the purge tank require disassembly to allow for repair and/or replacement of the valves and/or orifices. Further, if there are different thermal units, it may be necessary to have a different orifice size for optimal performance.